When the 1.2-megawatt battery made by Japan-based NGK Insulator began operating in Charleston in July 2006, it was the first megawatt-class sodium-sulfur, or NaS, battery to be used in North America.

The move was characterized as a breakthrough by Dana Waldo, president and chief operating officer of AEP subsidiary Appalachian Power.

“This battery and the other units we are considering putting on our system represent a significant step in making electricity more reliable and efficient for the future,” Waldo said at the time.

The utility installed the $2.5 million battery to postpone a costly upgrade of its “Chemical” substation near Charleston, according to AEP spokesman Pat D. Hemlepp.

“The area that that substation serves down in Charleston has growing demand, and we either had to do an extensive upgrade or put the battery there and delay that upgrade for six or seven years,” Hemlepp said. “Our view is it’s a better and less expensive solution to go with the battery.”

Appalachian Power charges the battery at night when demand is low.

It then runs the battery during high demand — times such as the hot afternoons of July and August — to supply 7.2 megawatt-hours of electricity, enough for at least 500 households for six or seven hours.

The success of the installation shows why utility-scale batteries have been sought for decades.

NGK worked with Tokyo Electric Power Co. to develop the NaS battery beginning in the mid-1980s, according to NGK’s Web site.

And a “vanadium redox” battery patented in Australia in 1986 has seen some commercial application, according to Brian D. Woerner, chairman of the Lane Department of Computer Science and Electrical Engineering at West Virginia University.

At $2,500 per kilowatt, AEP’s NaS battery cost more than the comparable capacity in a coal-fired power plant. But the two serve different purposes, Woerner said.

“We can get a lot more life out of our current system without having to add expensive new plants,” he pointed out. “It will be much more efficient and, in the long run, cheaper than it would otherwise be if we can use batteries to balance (peak demand).”

West Virginia and the nation will benefit from another much-anticipated advantage of utility-scale batteries, too. That advantage is increasing the viability of clean, renewable sources like wind power that are difficult for utilities to manage because they are intermittent.

“Solar energy is only available at those times the sun is shining — and that may not be in the middle of winter,” Woerner said. “Wind energy is only available when the wind is blowing, and that may not be in the middle of summer when you want to run all your air conditioners. Batteries give you the capability of taking advantage of those sources of energy when they’re available and storing them on a very large scale.”

Batteries may slow investment in new infrastructure, Woerner said, but they won’t prevent it entirely.

“In the long run, if we use 50 percent more energy several years from now, we’re probably still going to need more power plants and more transmission lines,” he said.

When AEP finally upgrades the Chemical substation, it will use its NaS battery elsewhere, Hemlepp said.

The utility plans to install a second, larger battery in West Virginia, likely in the Charleston area as well, and eventually expects to use batteries throughout its system—potentially increasing reliability in even the most remote areas.

“We could put an NaS battery on some more remote circuits like we have in West Virginia where, if there’s a pole or a line that gets knocked down, there’s no way to get power into the area at the other side of the incident,” Hemlepp said. “If you had an NaS battery at the end of the line, you could feed power back to the homes on the line.”